AbstractThe nature of reproductive barriers and meiotic behaviour of chromosomes were studied in interspecific hybrids among the six rough‐seededLupinusspecies. Out of 30 different interspecific crosses attempted in all possible combinations, eight produced viable F, seeds. These successful crosses involvedL. cosentinii, L. digitatus, L. atlanticusandL. pilosus.Crosses ofL. princeiwith other species resulted in shrivelled F, seed in all combinations. In contrast to previous reports, crosses ofL. palaestinuswith all other rough‐seeded lupins were incompatible as no F1hybrids were obtained. Barriers to interspecific reproduction were identified as nucleo‐cytoplasmic and embryo‐endosperm incompatibility in unsuccessful crosses, and chromosomal imbalances in F1hybrids. Gene transfer is possible amongL. cosentinii, L. digitatusandL. atlanticus, which produced F2seed. Patterns of chromosome configurations in F1meiotic cells suggested that these species have at least two genomes partially in common, but include inversions and translocations. The genome ofL. atlanticusis closer toL. digitatusthan toL. cosentinii, and that ofL. pilosusis closer toL. atlanticusthan toL. cosentinii. L. princeiappears to have an isolated genome within the rough‐seededLupin
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